(1) Field of the Invention
The present invention relates to a fuel injection apparatus for an internal combustion engine, more particularly to an improved fuel injection apparatus which includes an accumulator for storing the pressurized fuel while maintaining the pressure thereof at a predetermined high level, a fuel injection valve for injecting the pressurized fuel in the accumulator into a combustion chamber of the engine, and a pressurizing pump for pressurizing the fuel delivered from a fuel-feed pump and for supplying it into the accumulator through a check valve.
(2) Description of the Prior Art
In a conventional fuel injection apparatus for an internal combustion engine, a constant amount of fuel is kept pressurized by a pressurizing pump and delivered through a check valve into an accumulator. An external control unit outputs a signal to an injection valve to open and close it and thus control the injection amount and timing of the pressurized fuel.
When the accumulator is refilled with enough pressurized fuel to compensate for the consumption of the fuel by the injection valve, it has been necessary in prior art apparatuses to return any excessive fuel discharged from the pressurizing pump to a low pressure side, e.g., a fuel tank, through a relief valve. This means that the pressurizing pump in the prior art apparatus is always doing extra work. Such extra work not only means the pressurizing pump wastes energy, but also results in an unfavorable temperature rise of the fuel, increase of noise or vibration, and fluctuation of the fuel pressure.